<title>Adaptive optical 3D measurement with structured light</title>

Abstract

The described 3D-measurement system with fringe projection applies the principle of uniform scale representation by the exclusive use of phase-measurement values for the coordinates of each point. The object under test is successively illuminated with a grating structure from at least 3 different directions with a telecentric system, whereas gray-code is combined with four or five 90 degs phase-shifts. A CCD-camera records the intensity distribution of the fringes that appear as intersection lines on the surface of the object. This gives the linearly independent absolute phase values which are necessary for the calculation of the coordinates. It should be pointed out that all coordinates (x, y, z) are determined with the same accuracy. To compensate the influence of specular reflections or shadow areas up to 15 directions of light projection can be used. Moreover, the object can be rotated around a second axis yielding other views of the object. So we get different patches of the object that are transformed into a global coordinate system without any interactive user help. During this procedure correlation methods or special points are not necessary. The calibration of the 3D-orientation of the second axis is realized with a special calibration body.